The present invention relates to a cleaning apparatus and cleaning method for cleaning a photo-sensitive drum of, for example, an electrophotographic copying machine.
In the image forming apparatus of the electro-photographic copying machine or the like, a toner image corresponding to image data is formed on a photosensitive drum, and then, the toner image thus formed is transferred onto a paper sheet by a transfer charger. The toner left on the photosensitive drum after the toner image transfer is removed by a cleaning apparatus.
The cleaning apparatus has a cleaning blade. The toner left on the photosensitive drum is scraped by the tip or edge portion of the cleaning blade which is allowed in contact with the photosensitive drum. The toner scraped is captured by a recovery blade. The captured toner is fed to a recovery section with the aid of a paddle-form or a roller-form rotational body having a magnet.
In the image forming apparatus, the cleaning apparatus is placed at a side or above the photosensitive drum so as to face it.
When the cleaning apparatus is placed at a side of the photosensitive drum so as to face it, the toner scraped off by the tip portion of the cleaning blade falls under its own weight. No problem is posed in this case.
However, in the case where the cleaning apparatus is placed above the upper surface of the photosensitive drum so as to face it, the toner is more or less accumulated near the tip or edge portion of the cleaning blade, lowering a scraping performance (cleaning performance) of the cleaning blade.
It is possible to reduce the toner accumulation by enhancing a magnetic force of the magnet of the rotational body. In this case, however, an expensive material (ferrite etc.) having a high magnetic property must be used. As a result, the cost increases.
The present invention was made in view of the aforementioned circumstances. An object of the present invention is to provide a cleaning apparatus and cleaning method providing a good cleaning performance by reducing accumulation of a developing agent on a tip portion of the scraping member without requiring an expensive magnet.
A cleaning apparatus according to the present invention comprises:
a scraping means for removing a developing agent left on a rotatable image carrier, a tip portion of the scraping member being in contact with the rotatable image carrier;
a receiving means located at an upstream side of the scraping member in a rotation direction of the image carrier, for receiving the developing agent by the by bringing a tip portion of the scraping member in contact with the image carrier; and
a rotational body for feeding and recovering the developing agent received by the member by rotating the developing agent in a predetermined direction;
in which, assuming that a rotation center of the image carrier is 01, a rotation center of the rotational body is 02, a contact point of the image carrier in contact with the scraping member is A, a contact point of the image carrier in contact with the receipt member is B, and further
an angle between a line connecting the center 01 to the point A and a line connecting the center 01 to the center 02 is represented by a; and
an angle between the line connecting the center 01 to the point A and a line connecting the center 01 and point B is represented by b,
the rotational body is placed at a position satisfying an equation as to the angle a:
0xe2x89xa6axe2x89xa6b/2.
A cleaning apparatus according to the present invention comprises:
a scraping member for scraping a magnetic developing agent left on a rotatable image carrier by bringing a tip portion of the scraping member in contact with the rotatable image carrier;
a receipt member located at an upstream side of the scraping member in a rotation direction of the image carrier, for receiving the magnetic developing agent scraped by the scraping member by bringing a tip portion of the scraping member in contact with the image carrier; and
a magnetic rotational body for feeding and recovering the magnetic developing agent received by the receipt member by rotating the magnetic developing agent in a predetermined direction;
wherein, assuming that a rotation center of the image carrier is 01, a rotation center of the magnetic rotational body is 02, a contact point of the image carrier in contact with the scraping member is A, a contact point of the image carrier in contact with the receipt member is B, and further
an angle between a line connecting the center 01 to the point A and a line connecting the center 01 to the center 02 is represented by a; and
an angle between the line connecting the center 01 to the point A and a line connecting the center 01 and point B is represented by b,
the magnetic rotational body is placed at a position satisfying an equation as to the angle a:
0xe2x89xa6axe2x89xa6b/2.
A cleaning method according to the present invention comprises the steps of
scraping a developing agent left on a rotatable image carrier by a scraping member by bringing a tip portion of the scraping member in contact with the rotational image carrier;
receiving the developing agent scraped by the scraping member, by a receipt member which is positioned at an upstream side of the scraping member in a rotational direction of the image carrier by bringing a tip portion of the receipt member in contact with the image carrier; and
recovering the developing agent received by the receipt member by feeding in a predetermined direction with the aid of the rotational body,
wherein, assuming that a rotation center of the image carrier is 01, a rotation center of the rotational body is 02, a contact point of the image carrier in contact with the scraping member is A, a contact point of the image carrier in contact with the receipt member is B, and further
an angle between a line connecting the center 01 to the point A and a line connecting the center 01 to the center 02 is represented by a; and
an angle between the line connecting the center 01 to the point A and a line connecting the center 01 and point B is represented by b,
the rotational body is placed at a position satisfying an equation as to the angle a:
0xe2x89xa6axe2x89xa6b/2.